Fang Chao, Zhang Fei, Qiao Rui
Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, United States of America.
J Phys Condens Matter. 2018 Jun 6;30(22):224001. doi: 10.1088/1361-648X/aabead. Epub 2018 Apr 17.
The invasion of gas into liquid-filled nanopores is encountered in many engineering problems but is not yet well understood. We report molecular dynamics simulations of the invasion of methane gas into water-filled mica pores with widths of 2-6 nm. Gas invades into a pore only when the pressure exceeds a breakthrough pressure and a thin residual water film is left on the mica wall as the gas phase moves deeper into the pore. The gas breakthrough pressure of pores as narrow as 2 nm can be modeled reasonably well by the capillary pressure if the finite thickness of residual liquid water film and the liquid-gas interface are taken into account. The movement of the front of the liquid meniscus during gas invasion can be quantitatively described using the classical hydrodynamics when the negative slip length on the strongly hydrophilic mica walls is taken into account. Understanding the molecular mechanisms underlying the gas invasion in the system studied here will form the foundation for quantitative prediction of gas invasion in practical porous media.
气体侵入充满液体的纳米孔在许多工程问题中都会遇到，但目前尚未得到很好的理解。我们报告了甲烷气体侵入宽度为2 - 6纳米的充满水的云母孔隙的分子动力学模拟。只有当压力超过突破压力时，气体才会侵入孔隙，并且随着气相深入孔隙，云母壁上会留下一层薄的残余水膜。如果考虑残余液态水膜的有限厚度和液 - 气界面，对于窄至2纳米的孔隙，其气体突破压力可以通过毛细管压力得到合理的模拟。当考虑强亲水性云母壁上的负滑移长度时，气体侵入过程中液体弯月面的移动可以用经典流体力学进行定量描述。理解此处所研究系统中气体侵入的分子机制将为实际多孔介质中气体侵入的定量预测奠定基础。
